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How to create a backup chain
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Let's create a simple backup chain.

We're going to use `duplicity <https://duplicity.us/>`_ to upload everything in
``~/backup/`` to `Backblaze B2 storage <https://www.backblaze.com/cloud-storage>`_ - a
cost-effective solution which will be encrypted at rest, with 90-day rolling history.


Set up duplicity and B2
-----------------------

Backblaze have a great `tutorial
<https://www.backblaze.com/docs/cloud-storage-configure-backblaze-b2-with-duplicity-on-linux>`_
for setting up a B2 bucket and installing duplicity. The short version::

    sudo add-apt-repository ppa:duplicity-team/ppa
    sudo apt-get update
    sudo apt-get --only-upgrade install duplicity

Now lets create our local backup directory::

    mkdir -p ~/backup

The duplicity commands to backup everything in ``~/backup/`` to B2 with a 90 day history
will be::

    B2_URL="b2://[keyID]:[application key]@[B2 bucket name]"
    duplicity remove-older-than 90D -v9 --force $B2_URL
    duplicity --full-if-older-than 30D --copy-links ~/backup/ $B2_URL

You can download a fleshed out version of this from the runchain repo. Customise it then
install it as ``90-dup.sh``, so it will run at the end of the backup chain::

    wget https://raw.githubusercontent.com/radiac/runchain/refs/heads/main/samples/backup-dup.sh
    # Update the secrets in backup-dup.sh
    runchain add backup backup-dup.sh 90-dup.sh

We can test the backup with::

    runchain run backup

Lastly, let's schedule the chain to run at 2am every day::

    runchain cron backup "0 2 * * *"

Now everything in your ``~/backup`` directory will be backed up to B2 at 2am.


Back up a file or directory
---------------------------

Because we have ``--copy-links``, to back up a file or a directory, you can just symlink
it in::

    ln -s ~/uploads ~/backup/uploads


Back up something more complicated
----------------------------------

Let's see how we'd back up a PostgreSQL database running in a container.

Lets create ``dump-postgres.sh``::

    #!/bin/bash
    set -e
    docker exec postgres-container pg_dumpall > ~/backup/postgres_dump.sql

Now just add it to the ``backup`` chain before 90-dup.sh::

    runchain add backup dump-postgres.sh 50